Solve mima issue (by doubling private method definition)

Author: jchyb

compiler/src/dotty/tools/tasty/besteffort/BestEffortTastyHeaderUnpickler.scala

@@ -3,7 +3,7 @@ package dotty.tools.tasty.besteffort
 import java.util.UUID
 
 import BestEffortTastyFormat.{MajorVersion, MinorVersion, ExperimentalVersion, bestEffortHeader, header}
-import dotty.tools.tasty.{UnpicklerConfig, TastyHeaderUnpickler, TastyReader, UnpickleException, TastyFormat}
+import dotty.tools.tasty.{UnpicklerConfig, TastyHeaderUnpickler, TastyReader, UnpickleException, TastyFormat, TastyVersion}
 
 /**
  * The Best Effort Tasty Header consists of six fields:
@@ -33,7 +33,7 @@ sealed abstract case class BestEffortTastyHeader(
 )
 
 class BestEffortTastyHeaderUnpickler(config: UnpicklerConfig, reader: TastyReader) {
-  import TastyHeaderUnpickler._
+  import BestEffortTastyHeaderUnpickler._
   import reader._
 
   def this(reader: TastyReader) = this(UnpicklerConfig.generic, reader)
@@ -75,3 +75,101 @@ class BestEffortTastyHeaderUnpickler(config: UnpicklerConfig, reader: TastyReade
     if (!cond) throw new UnpickleException(msg)
   }
 }
+
+// Copy pasted from dotty.tools.tasty.TastyHeaderUnpickler
+// Since that library has strong compatibility guarantees, we do not want
+// to add any more methods just to support an experimental feature
+// (like best-effort compilation options).
+object BestEffortTastyHeaderUnpickler {
+
+  private def check(cond: Boolean, msg: => String): Unit = {
+    if (!cond) throw new UnpickleException(msg)
+  }
+
+  private def checkValidVersion(fileMajor: Int, fileMinor: Int, fileExperimental: Int, toolingVersion: String, config: UnpicklerConfig) = {
+    val toolMajor: Int = config.majorVersion
+    val toolMinor: Int = config.minorVersion
+    val toolExperimental: Int = config.experimentalVersion
+    val validVersion = TastyFormat.isVersionCompatible(
+      fileMajor            = fileMajor,
+      fileMinor            = fileMinor,
+      fileExperimental     = fileExperimental,
+      compilerMajor        = toolMajor,
+      compilerMinor        = toolMinor,
+      compilerExperimental = toolExperimental
+    )
+    check(validVersion, {
+      // failure means that the TASTy file cannot be read, therefore it is either:
+      // - backwards incompatible major, in which case the library should be recompiled by the minimum stable minor
+      //   version supported by this compiler
+      // - any experimental in an older minor, in which case the library should be recompiled by the stable
+      //   compiler in the same minor.
+      // - older experimental in the same minor, in which case the compiler is also experimental, and the library
+      //   should be recompiled by the current compiler
+      // - forward incompatible, in which case the compiler must be upgraded to the same version as the file.
+      val fileVersion = TastyVersion(fileMajor, fileMinor, fileExperimental)
+      val toolVersion = TastyVersion(toolMajor, toolMinor, toolExperimental)
+
+      val compat = Compatibility.failReason(file = fileVersion, read = toolVersion)
+
+      val what = if (compat < 0) "Backward" else "Forward"
+      val signature = signatureString(fileVersion, toolVersion, what, tool = Some(toolingVersion))
+      val fix = (
+        if (compat < 0) {
+          val newCompiler =
+            if (compat == Compatibility.BackwardIncompatibleMajor) toolVersion.minStable
+            else if (compat == Compatibility.BackwardIncompatibleExperimental) fileVersion.nextStable
+            else toolVersion // recompile the experimental library with the current experimental compiler
+          recompileFix(newCompiler, config)
+        }
+        else upgradeFix(fileVersion, config)
+      )
+      signature + fix + tastyAddendum
+    })
+  }
+
+  private def signatureString(
+      fileVersion: TastyVersion, toolVersion: TastyVersion, what: String, tool: Option[String]) = {
+    val optProducedBy = tool.fold("")(t => s", produced by $t")
+    s"""$what incompatible TASTy file has version ${fileVersion.show}$optProducedBy,
+      |  expected ${toolVersion.validRange}.
+      |""".stripMargin
+  }
+
+  private def recompileFix(producerVersion: TastyVersion, config: UnpicklerConfig) = {
+    val addendum = config.recompileAdditionalInfo
+    val newTool = config.upgradedProducerTool(producerVersion)
+    s"""  The source of this file should be recompiled by $newTool.$addendum""".stripMargin
+  }
+
+  private def upgradeFix(fileVersion: TastyVersion, config: UnpicklerConfig) = {
+    val addendum = config.upgradeAdditionalInfo(fileVersion)
+    val newTool = config.upgradedReaderTool(fileVersion)
+    s"""  To read this ${fileVersion.kind} file, use $newTool.$addendum""".stripMargin
+  }
+
+  private def tastyAddendum: String = """
+  |  Please refer to the documentation for information on TASTy versioning:
+  |  https://docs.scala-lang.org/scala3/reference/language-versions/binary-compatibility.html""".stripMargin
+
+  private object Compatibility {
+    final val BackwardIncompatibleMajor = -3
+    final val BackwardIncompatibleExperimental = -2
+    final val ExperimentalRecompile = -1
+    final val ExperimentalUpgrade = 1
+    final val ForwardIncompatible = 2
+
+    /** Given that file can't be read, extract the reason */
+    def failReason(file: TastyVersion, read: TastyVersion): Int =
+      if (file.major == read.major && file.minor == read.minor && file.isExperimental && read.isExperimental) {
+        if (file.experimental < read.experimental) ExperimentalRecompile // recompile library as compiler is too new
+        else ExperimentalUpgrade // they should upgrade compiler as library is too new
+      }
+      else if (file.major < read.major)
+        BackwardIncompatibleMajor // pre 3.0.0
+      else if (file.isExperimental && file.major == read.major && file.minor <= read.minor)
+        // e.g. 3.4.0 reading 3.4.0-RC1-NIGHTLY, or 3.3.0 reading 3.0.2-RC1-NIGHTLY
+        BackwardIncompatibleExperimental
+      else ForwardIncompatible
+  }
+}

tasty/src/dotty/tools/tasty/TastyHeaderUnpickler.scala

@@ -133,7 +133,7 @@ object TastyHeaderUnpickler {
     if (!cond) throw new UnpickleException(msg)
   }
 
-  private[tasty] def checkValidVersion(fileMajor: Int, fileMinor: Int, fileExperimental: Int, toolingVersion: String, config: UnpicklerConfig) = {
+  private def checkValidVersion(fileMajor: Int, fileMinor: Int, fileExperimental: Int, toolingVersion: String, config: UnpicklerConfig) = {
     val toolMajor: Int = config.majorVersion
     val toolMinor: Int = config.minorVersion
     val toolExperimental: Int = config.experimentalVersion